A gas-engine generator includes an engine operated with gas as fuel, a generator generating electricity from an engine output, a fuel system supplying gas fuel to the engine, and an exhaust system exhausting exhaust gas from the engine.
Conventionally, a fuel system in a portable gas-engine generator includes a manual fuel cock provided for supplying depressurized gas fuel from a gas cylinder, etc., an on-off valve provided for supplying the gas fuel to an engine side, a vaporizer heating the gas fuel to gasify it, a mixer mixing supply gas and air, and a zero governor that controls a pressure of fuel to be supplied to the mixer to a constant value. A negative cock is provided integrally with the on-off valve, allowing the on-off valve to open by a negative pressure in a crank case of the engine, whereby the gas is supplied to the engine side only when the engine is in operation.
The portable gas-engine generator is easily turned over because of its small size and light weight and, when the negative pressure in the crank case is used as a negative pressure for operating the negative pressure cock, lubricant in the crank case may enter into the negative cock at the time of turnover (disadvantageous flowing of lubricant may occur) to cause malfunction.
To avoid this, as described in, e.g., JP 2011-85118 A, there is proposed a structure in which a breather chamber is provided separately from the crank case for the purpose of taking out the negative pressure, so as to prevent the lubricant from entering the negative pressure cock at the time of turnover.